Today's Message Index:
----------------------
1. 02:22 AM - Trigger for NTSB letter (David Johnson)
2. 05:56 AM - HD/HDS cable specs (Jeff)
3. 07:01 AM - Re: Thoughts regarding Flutter (jaybannist@cs.com)
4. 08:40 AM - Re: Trigger for NTSB letter (Bryan Martin)
5. 09:10 AM - Re: Thoughts regarding Flutter (Bryan Martin)
6. 11:23 AM - Re: Thoughts regarding Flutter (NYTerminat@aol.com)
7. 12:03 PM - Re: Thoughts regarding Flutter (Craig Payne)
8. 04:23 PM - Re: Thoughts regarding Flutter (T. Graziano)
9. 08:11 PM - Cable tensions for the HDS (LarryMcFarland)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Trigger for NTSB letter |
There seems to be an awful lot of speculation (and anger) about who got
the NTSB interested in the 601XL. Most of it seems to be directed at the
ZBAG group.
No-one seems to have mentioned the letter that the Dutch authorities
sent to all civil aviation authorities around the world, basically
saying that the 601XL is not fit to fly.
Whether this went to the NTSB or the FAA (if the latter, then I would
expect them to pass it on to the NTSB for comment), it is not something
that any bureaucrat could or would ignore.
I don't have the content of the letter, but notification of it was
published on the Zenair Europe website.
http://www.zenairulm.com/News/index_files/Page972.htm
They have published their response, but I believe that it was only sent
to European authorities.
Dave Johnson
Ready to test fly - grounded - in limbo (and NOT HAPPY!!)
do not archive
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | HD/HDS cable specs |
Roger,
Edition 3 dated Jan. 1995 of the CH 601 (HD) Construction Manual gives
the cables tension as "30 to 40 lbs." on page 29. Since the HDS plans were
an addendum to this manual, I presume the same tension applies to the HDS.
As far as I know, the cable runs were exactly the same for the HDS as for
the HD.
Jeff Davidson
Howdy all;
I have my annual inspection on Saturday, and for the life of me I can't find
the 601 HDS cable tension specs. Does anyone know what the elevator and
rudder cables should be tension to on a 601 hds?
Thanks
Roger
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Thoughts regarding Flutter |
Tony,
I happen to agree with you.? I also think that the elevator is a more likely source
of trouble than the ailerons.? Even though the XL that I flew didn't seem
to me to have an overly sensitive elevator, I have read and heard comments that
indicates that it is troublesome to others. The NTSB letter goes into some
detail about the elevator being progressively effective.? It is fairly well accepted
that excessive elevator input can overstress an airframe. In the case of
the XL accidents, a gross elevator movement could very well have overstressed
the wings and made them fail.? The NTSB accident report of the Yuba accident
speculated that the first thing to fail was the horizontal stabilizer, in a downward
direction.? It seems to me that a max down elevator could have caused
that. I did not see any mention of whether the Heintz recommended elevator stop
had been added to this airplane.
This makes me wonder if adding progressive resistance to fore and aft movement
of the stick might make sense to defeat the progressive effectiveness of the elevator,
ie: bungees or springs. what do you think?
Jay Bannister
-----Original Message-----
From: T. Graziano <tonyplane@bellsouth.net>
Sent: Fri, 17 Apr 2009 11:32 pm
Subject: Re: Zenith601-List: Thoughts regarding Flutter
?
Additional thoughts, Scott?
?
Sounds reasonable.? I thought about replacing
cables with push rods, but then thought that the natural freq of a rod would
probably be lower than a tensioned cable and more likely to
resonate.
?
Today as I was up enjoying the sky in my XL, I
crossed mid-field and broke to down wind and it reminded my of another
reconstructed crash at the crash lab at March AFB during a course I took in
Aircraft Accident Investigation at USC thirty years ago.
It was an AeroCommander Twin that shed its
wings.?
?
The physical investigator?instructor, (who was
also my undergraduate instructor in Rotary Wing Aerodynamics years prior)
related that he was requested to investigate the wing failure of another Twin
Commander, I believe that occurred in Co.? If I recall correctly, the
Commander made a mid-field crossing and broke to down wind and had a wing
structural failure which was attributed to pilot error causing the
overload.? The instructor related that there were also other
Commanders?that?had had the same failure.
?
What he discovered (and I have the plot somewhere
in my class notes, buried ?) was that the stick forces per?G went NEGATIVE
at about 4 Gs.? Imagine the yoke coming back in your lap?and the wing
fails due to overload, if above Va. (There was an AD issued to require a weight
in the control system to pull the stick under G loading?(bob
weights?have been ?used?in many aircraft control
systems).
?
The reason I bring this up is that I still believe
the XL light stick forces can easily result excessive G loading and are quite
possibly the?REAL reason for the wing failures.? Not that light stick
forces are bad, but one has to not be ham fisted above Va. (I previously related
giving an older pilot a ride in my XL during a pretty turbulent day and he
pushed the stick rapidly nose down?such that I would have gone through the
canopy without a seat belt.? This happened during climb out? at about
80 - 90kts and the gusty conditions had caused a pitch up.(still can not believe
another pilot would have done that, but possibly his Tomahawk had a much
different elevator response).?
?
Somehow, some people jumped on the flutter
bandwagon, and as another matronics "inputer" stated - "and so it
was"
?
What really concerns me is that the NTSB might wish
to make a "Science Project" (Note)?over additional flutter testing of the
XL. They evidently do not wish to accept the successful flutter tests
already done by Zenith (see page 6 of the NTSB
report).???????????????????????????????????????????????????????????????
???????????????????????????????????????????????????????
Note:
?????????????
A Science Project is where you spend all of your?resources but never come
up with a result that is acceptable to the government because additional tests
or analytical parameters are ALWAYS?required. ("You only tested (or
modeled)?down to -40F.? We?require additional testing at -65F
.......and on ....and on ..and ..............").?
?
Tony Graziano
Buchanan, Tn
XL/Jab; N493TG; 483 really great hours in?my
XL
?
?
________________________________________________________________________
Email message sent from CompuServe - visit us today at http://www.cs.com
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Trigger for NTSB letter |
Unfortunately, the Dutch report that started that grounding was
seriously flawed. For instance, one of the accidents cited in that
report (in England) didn't even involve a 601XL but rather a 601UL
that was obviously the result of the pilot mishandling the aircraft.
That report was released before any significant investigation into the
Dutch accident had been done. It's almost like the author of that
report simply did some cursory research into the design and came
across all the rumor, innuendo and ignorant speculation circulating
around the net at that time, and based his report on that information.
And now, aviation authorities in several other countries are taking
action based in part on that flawed Dutch report. Has anybody ever
heard the term "garbage in, garbage out"?
One of the three greatest lies in history: "I'm from the government,
I'm here to help you."
On Apr 18, 2009, at 5:19 AM, David Johnson wrote:
> There seems to be an awful lot of speculation (and anger) about who
> got the NTSB interested in the 601XL. Most of it seems to be
> directed at the ZBAG group.
>
> No-one seems to have mentioned the letter that the Dutch authorities
> sent to all civil aviation authorities around the world, basically
> saying that the 601XL is not fit to fly.
>
> Whether this went to the NTSB or the FAA (if the latter, then I
> would expect them to pass it on to the NTSB for comment), it is not
> something that any bureaucrat could or would ignore.
>
> I don't have the content of the letter, but notification of it was
> published on the Zenair Europe website.
>
> http://www.zenairulm.com/News/index_files/Page972.htm
>
> They have published their response, but I believe that it was only
> sent to European authorities.
>
> Dave Johnson
>
> Ready to test fly - grounded - in limbo (and NOT HAPPY!!)
>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Thoughts regarding Flutter |
Another thing to consider is that the CG of the 601XL shifts rearward
as you burn off fuel. So If you make a long cross country flight in a
heavily loaded XL, you may discover that the pitch sensitivity has
increased significantly when it comes time to land. I have had this
experience myself. I was a little surprised when the plane started to
porpoise on short final. I realized what was happening and got it
settled down fairly quickly, but it did get my attention. I sure am
glad I spent the extra money for the confor-foam seats cushions. I can
spend four hours in the plane without getting greatly fatigued.
I added a bungee cord to the elevator controls to assist with nose up
trim. One of these days, I'm going to link it to the flap torque tube
to provide some automatic trim adjustment with flap deployment.
On Apr 18, 2009, at 9:58 AM, jaybannist@cs.com wrote:
> Tony,
>
> I happen to agree with you. I also think that the elevator is a
> more likely source of trouble than the ailerons. Even though the XL
> that I flew didn't seem to me to have an overly sensitive elevator,
> I have read and heard comments that indicates that it is troublesome
> to others. The NTSB letter goes into some detail about the elevator
> being progressively effective. It is fairly well accepted that
> excessive elevator input can overstress an airframe. In the case of
> the XL accidents, a gross elevator movement could very well have
> overstressed the wings and made them fail. The NTSB accident report
> of the Yuba accident speculated that the first thing to fail was the
> horizontal stabilizer, in a downward direction. It seems to me that
> a max down elevator could have caused that. I did not see any
> mention of whether the Heintz recommended elevator stop had been
> added to this airplane.
>
> This makes me wonder if adding progressive resistance to fore and
> aft movement of the stick might make sense to defeat the progressive
> effectiveness of the elevator, ie: bungees or springs. what do you
> think?
>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Thoughts regarding Flutter |
But weren't some of these accidents straight and level?
Bob Spudis
In a message dated 4/18/2009 12:10:49 P.M. Eastern Daylight Time,
bryanmmartin@comcast.net writes:
--> Zenith601-List message posted by: Bryan Martin
<bryanmmartin@comcast.net>
Another thing to consider is that the CG of the 601XL shifts rearward
as you burn off fuel. So If you make a long cross country flight in a
heavily loaded XL, you may discover that the pitch sensitivity has
increased significantly when it comes time to land. I have had this
experience myself. I was a little surprised when the plane started to
porpoise on short final. I realized what was happening and got it
settled down fairly quickly, but it did get my attention. I sure am
glad I spent the extra money for the confor-foam seats cushions. I can
spend four hours in the plane without getting greatly fatigued.
I added a bungee cord to the elevator controls to assist with nose up
trim. One of these days, I'm going to link it to the flap torque tube
to provide some automatic trim adjustment with flap deployment.
On Apr 18, 2009, at 9:58 AM, jaybannist@cs.com wrote:
> Tony,
>
> I happen to agree with you. I also think that the elevator is a
> more likely source of trouble than the ailerons. Even though the XL
> that I flew didn't seem to me to have an overly sensitive elevator,
> I have read and heard comments that indicates that it is troublesome
> to others. The NTSB letter goes into some detail about the elevator
> being progressively effective. It is fairly well accepted that
> excessive elevator input can overstress an airframe. In the case of
> the XL accidents, a gross elevator movement could very well have
> overstressed the wings and made them fail. The NTSB accident report
> of the Yuba accident speculated that the first thing to fail was the
> horizontal stabilizer, in a downward direction. It seems to me that
> a max down elevator could have caused that. I did not see any
> mention of whether the Heintz recommended elevator stop had been
> added to this airplane.
>
> This makes me wonder if adding progressive resistance to fore and
> aft movement of the stick might make sense to defeat the progressive
> effectiveness of the elevator, ie: bungees or springs. what do you
> think?
>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
**************Access 350+ FREE radio stations anytime from anywhere on the
web. Get the Radio Toolbar!
(http://toolbar.aol.com/aolradio/download.html?ncid=emlcntusdown00000003)
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Thoughts regarding Flutter |
> One of these days, I'm going to link it to the flap torque tube to provide
some automatic trim adjustment with flap deployment.
There is a little box that does this (although you might consider it
overkill):
http://www.aircraftextras.com/
-- Craig
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Thoughts regarding Flutter |
Jay,
What commonly has been done is to add a mass to the bottom of the stick
assembly, usually Tungsten or depleted Uranium to save space. As you
change the angle of the stick, the mass tends to pull the stick
relatively straight neutral and the more G loads the more force exerted
by the mass to center the stick relatively neutral, ---- the more Gs
pulled, the more force it takes to hold back the stick; stick forces per
G goes up. I don't know if the geometry of the XLs "stick
configuration" would permit a mass addition.
The Yuba City with the stab failure in a down direction indicates UP
elevator. Once the stab fails, the nose pitches violently down, and the
wing fails in a relatively down direction - excessive negative Gs. In a
good design, it would be a toss up as to what fails first under
excessive G loading, the stab or the wing.
I believe the Yuba City wing failure speaks volumes about an overstress
condition caused by stick input
Tony.
----- Original Message -----
From: jaybannist@cs.com
To: zenith601-list@matronics.com
Sent: Saturday, April 18, 2009 8:58 AM
Subject: Re: Zenith601-List: Thoughts regarding Flutter
Tony,
I happen to agree with you. I also think that the elevator is a more
likely source of trouble than the ailerons. Even though the XL that I
flew didn't seem to me to have an overly sensitive elevator, I have read
and heard comments that indicates that it is troublesome to others. The
NTSB letter goes into some detail about the elevator being progressively
effective. It is fairly well accepted that excessive elevator input can
overstress an airframe. In the case of the XL accidents, a gross
elevator movement could very well have overstressed the wings and made
them fail. The NTSB accident report of the Yuba accident speculated
that the first thing to fail was the horizontal stabilizer, in a
downward direction. It seems to me that a max down elevator could have
caused that. I did not see any mention of whether the Heintz recommended
elevator stop had been added to this airplane.
This makes me wonder if adding progressive resistance to fore and aft
movement of the stick might make sense to defeat the progressive
effectiveness of the elevator, ie: bungees or springs. what do you
think?
Jay Bannister
-----Original Message-----
From: T. Graziano <tonyplane@bellsouth.net>
To: zenith601-list@matronics.com
Sent: Fri, 17 Apr 2009 11:32 pm
Subject: Re: Zenith601-List: Thoughts regarding Flutter
Additional thoughts, Scott
Sounds reasonable. I thought about replacing cables with push rods,
but then thought that the natural freq of a rod would probably be lower
than a tensioned cable and more likely to resonate.
Today as I was up enjoying the sky in my XL, I crossed mid-field and
broke to down wind and it reminded my of another reconstructed crash at
the crash lab at March AFB during a course I took in Aircraft Accident
Investigation at USC thirty years ago.
It was an AeroCommander Twin that shed its wings.
The physical investigator instructor, (who was also my undergraduate
instructor in Rotary Wing Aerodynamics years prior) related that he was
requested to investigate the wing failure of another Twin Commander, I
believe that occurred in Co. If I recall correctly, the Commander made
a mid-field crossing and broke to down wind and had a wing structural
failure which was attributed to pilot error causing the overload. The
instructor related that there were also other Commanders that had had
the same failure.
What he discovered (and I have the plot somewhere in my class notes,
buried ?) was that the stick forces per G went NEGATIVE at about 4 Gs.
Imagine the yoke coming back in your lap and the wing fails due to
overload, if above Va. (There was an AD issued to require a weight in
the control system to pull the stick under G loading (bob weights have
been used in many aircraft control systems).
The reason I bring this up is that I still believe the XL light stick
forces can easily result excessive G loading and are quite possibly the
REAL reason for the wing failures. Not that light stick forces are bad,
but one has to not be ham fisted above Va. (I previously related giving
an older pilot a ride in my XL during a pretty turbulent day and he
pushed the stick rapidly nose down such that I would have gone through
the canopy without a seat belt. This happened during climb out at
about 80 - 90kts and the gusty conditions had caused a pitch up.(still
can not believe another pilot would have done that, but possibly his
Tomahawk had a much different elevator response).
Somehow, some people jumped on the flutter bandwagon, and as another
matronics "inputer" stated - "and so it was"
What really concerns me is that the NTSB might wish to make a "Science
Project" (Note) over additional flutter testing of the XL. They
evidently do not wish to accept the successful flutter tests already
done by Zenith (see page 6 of the NTSB report).
Note:
A Science Project is where you spend all of your
resources but never come up with a result that is acceptable to the
government because additional tests or analytical parameters are ALWAYS
required. ("You only tested (or modeled) down to -40F. We require
additional testing at -65F .......and on ....and on ..and
..............").
Tony Graziano
Buchanan, Tn
XL/Jab; N493TG; 483 really great hours in my XL
-------------------------------------------------------------------------
-----
Email message sent from CompuServe - visit us today at
http://www.cs.com
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Cable tensions for the HDS |
Jeff,
Within the Construction Manual for the Zodiac Ch 601, the required cable
tension is stated "cable tension 30 - 40 lbs."
Larry McFarland 601HDS at www.macsmachine.com
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|